Dual connectivity mode of operation of a user equipment in a wireless communication network

ABSTRACT

A system and method provide a security aspect for a UE in dual connectivity mode of operation in wireless communication networks. The system and method provide secure simultaneous transmission and reception in a secure manner between a User Equipment (UE) and one or more eNodeBs (eNBs) configured in an inter-eNB carrier aggregation scenario. The system establishes of a security context between the UE and the Secondary eNB (SeNB) using the RRC signaling between the UE and the Master eNB (MeNB), when a plurality of SCells within SeNB are added simultaneously. The system also detects the intruder in the user data radio bearers, while a UE is operating in dual connectivity mode of operation.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of application Ser. No. 16/532,130,filed Aug. 5, 2019, which is a continuation of application Ser. No.16/111,730, filed Aug. 24, 2018, now U.S. Pat. No. 10,375,571, which isa continuation of application Ser. No. 14/599,928 filed Jan. 19, 2015,now U.S. Pat. No. 10,064,051, which claims priority to provisionalspecification of Indian Application Number 202/CHE/2014, filed Jan. 17,2014, Indian Application Number 1540/CHE/2014, filed Mar. 24, 2014, andcomplete specification of Indian Application Number 202/CHE/2014, filedJan. 13, 2015, the disclosures of which are hereby incorporated byreference herein.

BACKGROUND 1. Field

The present application relates to the field of wireless communicationand more particularly to security aspect for a User Equipment (UE) indual connectivity mode of operation in wireless communication networks.

2. Description of Related Art

With rise in deployment of Long term Evolution (LTE) and LTE advanced(LTE-A), small cells using low power nodes such as a Pico cell and aFemto cell are considered promising to cope with mobile trafficexplosion. A small cell using a low power node, which has transmissionpower (Tx) lower than macro node and Base Station (BS) classes, ispreferred for hotspot deployments in indoor and outdoor scenariosresulting in enhanced performance.

The small cell enhancement for Evolved Universal MobileTelecommunication System (UMTS) Terrestrial Radio Access Network(E-UTRAN) and E-UTRA focuses on additional functionalities for enhancedperformance in hotspot areas for indoor and outdoor using the low powernodes.

The 3^(rd) Generation Partnership Project (3GPP) is considering use ofpotential higher layer technologies for enhanced support of small celldeployments in Evolved (Universal Mobile Telecommunications System(UMTS) Terrestrial Radio Access (E-UTRA) and E-Evolved UMTS TerrestrialRadio Access Network (UTRAN) to fulfill the deployment scenarios and therequirements specified in TR 36.932.

3GPP is considering a deployment scenario, in which different frequencybands are separately assigned to macro layer and small cell layer,respectively. Small cell enhancement is expected to supportsignificantly increased user throughput for both downlink and uplinkwith main focus on typical user throughput, considering a reasonablesystem complexity. Small cell enhancement is expected to target thecapacity per unit area (such as in bps/km2) to be as high as possible,for a given user and small cell distribution, typical traffic types andconsidering a reasonable system complexity. The small cell enhancementsare also expected to consider the impact of the actual backhaul delaysand provide solutions with the aim of improved system performance. Otheraspects, for example service quality of Voice over Long Term Evolution(LTE) (VoLTE), such as Mean Opinion Score (MOS) and delay or jitterimpacts on services, such as video streaming, video calls and so forth,could also be addressed later.

In LTE Release-10 carrier aggregation, all the component carriersinvolved in carrier aggregation is handled at the same evolved NodeB(eNB) (co-located) and the component carriers are from the samefrequency band i.e. intra-band carrier aggregation. In LTE Release-11specification supports inter-band carrier aggregation where thecomponent carriers are from different frequency bands. In the inter-bandcarrier aggregation scenario the component carrier (F1) from a lowerfrequency band can provide coverage and mobility whereas the othercomponent carrier (F2) from a higher frequency band can provide highthroughput to the User Equipment (UE). The inter-band carrieraggregation could be non-co-located, where the UE is carrier aggregatedwith at least one first serving frequency by a Master eNB (MeNB) and atleast one second serving frequency served by a Secondary eNB (SeNB).When carrier aggregation between at least one cell controlled by twogeographically separated eNBs is envisioned then it is called asinter-eNB carrier aggregation and the UE is said to be configured withdual connectivity mode of operation. In such a scenario, dualconnectivity is envisioned such that the UE maintains physical linkswith at least one cell controlled by two geographically separated eNBs.The UE maintains dual connectivity both in downlink and uplink or onlydownlink. In uplink the dual connectivity towards the MeNB and the SeNBcould be simultaneous or could be time multiplexed.

In the so-called dual connectivity mode of operation, the UE consumesradio resources provided by two different network nodes, namely MeNBassociated with at least one first serving frequency and SeNB associatedwith at least one second serving frequency, connected via a non-idealbackhaul interface, such as X2 interface. The MeNB is the eNB that hoststhe Radio Resource Control (RRC) layer and a single S1-MME terminationpoint exists for a UE configured with dual connectivity mode ofoperation between the Mobile Management Entity (MME) and the E-UTRAN.The MeNB, therefore, acts as a mobility anchor towards the core network(CN). The E-UTRAN architecture and related functions to support DualConnectivity for E-UTRAN is further described in TS 36.300.

In existing security mechanisms for single connectivity or UE supportingRelease-10 or Release-11 carrier aggregation, authentication andauthorization are performed using the authentication and key agreementprocedure (AKA) defined for the evolved Universal Terrestrial RadioAccess Network (E-UTRAN) in the LTE Networks. An initial security key isderived by the Mobility Management Entity (MME) in the core network andsent to a serving or source eNB of the UE. During an inter-eNB (S1 orX2-intiated) handover, the serving eNB derives the security key for atarget eNB, using a base security key (if an interface such as an X2interface exists between the serving eNB and the target eNB), to whichthe UE is handed over due to mobility. The security key provided by theserving eNB is used for deriving further keys in the target eNB, whichare used for user plane data protection (same like serving eNB, UEderives the security key and further keys like target eNB).

During a handover (HO), using vertical key derivation, that is, theunused next hop (NH) parameters can be used for deriving the basesecurity key at the source eNB (when S1 interface is involved in HOprocedure). For dual connectivity, the existing procedure using verticalkey derivation, a new security key associated with the secondary eNB(SeNB) for the UE can be derived at the Master eNB (MeNB) using unusedNext Hop (NH) parameters. However, the unused NH parameters may not bealways available at the MeNB to derive the security key associated withSeNB using vertical key derivation. In existing security mechanismduring HO an existing security key associated with the source eNB can beused for deriving the base security key. For dual connectivity, thisprinciple can be extended such that the existing security key of theMeNB can be used as for deriving the security key for the SeNB. The useof the MeNB security key for deriving the security key of SeNB forsecuring the communication between the SeNB and the UE may not provideadequate key separation and also possible key stream repetition issue,resulting in security compromise.

Further, if the MeNB derives security key for the SeNB using an existingsecurity key, then the key repetition will occur. For example, if eachtime the same SeNB is removed and added again for supporting dualconnectivity, the security key generated may be repeated. Further keyrepetition may also occur if the first SeNB is removed and anotherdifferent second SeNB is added, but the first SeNB and second SeNBoperate on the same frequency and have the same physical cell identity(PCI). Another scenario for key repetition occurrence is when the userplane data handled by the data radio bearer (DRB) established on theSeNB experience PDCP COUNT wrap around (that is, when same PDCP Countvalue with same DRB-ID and security key are used again (more than once),it is possible to derive the key stream or message details). Therefore,key stream repetition is highly possible when the existing securitymechanism defined in TS 33.401 is used for dual connectivity and leadsto exposing the user plane to security attacks, which needs to beavoided.

In addition to key repetition, the security capabilities and/or localconfiguration of the SeNB may be different from the MeNB. Hence, the UEconfigured with dual connectivity may need to use differentcryptographic algorithms for communicating with the SeNB. Theestablishment of security context between the SeNB and the UE requiresknowledge of the security algorithms supported and selected by the MeNB.

When there is no restriction to add only one SCell in the SeNB at atime, that is, it is allowed to add more than one SCell in the SeNB atinitial configuration of the SeNB, then using the existing HO securitymechanism for Dual connectivity, the MeNB should know the PCI andoperating downlink frequency (EARFCN-DL) of one of the SCell within theSeNB to be used to derive the security key for the SeNB.

When the PDCP count of any PDCP entity handling the DRB in MeNB is aboutto wrap around then the MeNB could initiate intra-cell handover (i.e.,handover to the same MeNB cell) to refresh the MeNB key, then the MeNBwould have to release all the SCells in the SeNB at the same time inorder to ensure that security key of SeNB is also updated (based onrefreshed MeNB key). When the security key of the MeNB is updated whilethe SeNB continues to use existing security key that was derived fromprevious security key of the MeNB, then this may result in securitycompromise and, hence, it is not a good security practice (to usesecondary keys derived from primary key which is invalidated). When thePDCP count of any PDCP entity handling the DRB in the SeNB is about towrap around, then key repetition occurrence is possible when the userplane data handled by the data radio bearer (DRB) established on theSeNB experience PDCP COUNT wrap around (that is same PDCP Count valuewith same DRB-ID and security key are used again (more than once)).

Limitations and disadvantages exist in the operation and management ofsecurity mechanism such as countercheck procedure execution for DRBestablished in the SeNB for a UE configured with dual connectivity modeof operation that can lead to a potential compromise in security.Existing countercheck procedure does not address the issue of intruderdetection in dual connectivity, as the SeNB does not have direct RRCsignaling connection with the UE. There needs to be a method to checkthe PDCP counter associated with the SeNB, for whether an packetinjection attack is mounted and also possibly flag the DRB-IDs with theindication indicating which node is responsible for handling the DRB andproviding the UE the means to identity the correct DRB context used inthe MeNB or SeNB.

In legacy LTE systems (namely, Release 8 to Release 11), thecountercheck procedure is specified in 3GPP specification TS 36.331(section 5.3.6) for detecting packet injection attack, where the RRCprocedure is kind of audit where eNB checks if the PDCP COUNT providedby the UE for the established DRBs match with the values sent by the eNBin the request message of the procedure. If such an intruder attack isdetected, then the network can decide to release the RRC connectionimmediately and can initiate other procedure like informing network nodeabout the attack. For Release-10 carrier aggregation (CA), the primarycell (PCell) of the UE initiates the countercheck procedure for the DRBestablished on the SCell(s). This principle cannot be applied for dualconnectivity where the RRC layer sits in the MeNB and there is nocontext or information about the PDCP entity in the SeNB available withthe MeNB.

Compared to Release-10 CA, the extension of countercheck procedure fordual connectivity requires new signaling support on the X2 interface andalso in the RRC signaling between the UE and the MeNB.

SUMMARY

The aspect of the embodiments herein is to provide secure simultaneoustransmission and reception in a secure manner between a User Equipment(UE) and one or more eNodeBs (eNBs) configured in an inter-eNB carrieraggregation scenario.

Another aspect of the disclosure is to propose methods and systems forestablishment of a security context between the UE and the SeNB usingthe RRC signaling between the UE and the MeNB, when a plurality ofSCells within SeNB are added simultaneously.

Another aspect of the disclosure is to propose methods and systems forestablishment or updating of a security context between the UE and theSeNB using the X2 signaling between the MeNB and SeNB and RRC signalingbetween the UE and the MeNB, when the PDCP COUNT of at least one DRBestablished on at least one second serving frequency served by the SeNBis about to wrap around.

Another aspect of the disclosure is to propose methods and systems forestablishment or updating of a security context between the UE and theSeNB using the X2 signaling between the MeNB and SeNB and RRC signalingbetween the UE and the MeNB, when the SCell configured for the UE withPUCCH resources on at most one second serving frequency served by theSeNB is changed.

Another aspect of the disclosure is to propose methods and systems forestablishment or updating of a security context between the UE and theSeNB using the X2 signaling between the MeNB and SeNB and RRC signalingbetween the UE and the MeNB, when the cryptographic algorithms used bythe UE and the SeNB to be changed.

Another aspect of the disclosure is to propose a mechanism to detect theintruder (packet injection) in the data radio bearers using the X2signaling between the MeNB and SeNB and RRC signaling between the UE andthe MeNB, when the UE is operating in dual connectivity mode ofoperation.

In accordance with an aspect of the present disclosure, a method isprovided for performing a change of a serving cell group (SCG) in awireless communication system supporting a dual connectivity of a userequipment, the method comprises transmitting, by a secondary basestation for the dual connectivity, a message including informationindicating the change of the SCG to a master base station for the dualconnectivity, to perform the change of the SCG, and receiving, by thesecondary base station, a security key associated with the secondarybase station, the security key being refreshed by the change of the SCG.

In accordance with another aspect of the present disclosure, a secondarybase station is provided for performing a change of a serving cell group(SCG) in a wireless communication system supporting a dual connectivityof a user equipment, the secondary base station comprises acommunication interface configured to communicate with other networkentity, and a controller configured to control transmitting a messageincluding information indicating the change of the SCG to a master basestation for the dual connectivity, to perform the change of the SCG, andreceiving a security key associated with the secondary base station, thesecurity key being refreshed by the change of the SCG.

In accordance with further aspect of the present disclosure, a method isprovided for performing packet data convergence protocol (PDCP) countercheck of a serving cell group (SCG) in a wireless communication systemsupporting a dual connectivity of a user equipment, the method comprisesreceiving, by a master base station for the dual connectivity, a requestmessage including information for checking a PDCP count from a secondarybase station for the dual connectivity, the PDCP count being associatedwith a SCG radio bearer of the secondary base station, and performing,by the master base station in response to the request message, a PDCPcounter check procedure to verify a value of the PDCP count, based onthe received information.

In accordance with further aspect of the present disclosure, a masterbase station is provided for performing packet data convergence protocol(PDCP) counter check of a serving cell group (SCG) in a wirelesscommunication system supporting a dual connectivity of a user equipment,the base station comprises a communication interface configured tocommunicate with other network entity, and a controller configured tocontrol receiving a request message including information for checking aPDCP count from a secondary base station for the dual connectivity, thePDCP count being associated with a SCG radio bearer of the secondarybase station, and performing, in response to the request message, a PDCPcounter check procedure to verify a value of the PDCP count, based onthe received information.

Also, provided herein is a method for creating a secure connection for aUser Equipment (UE) in a wireless communication network operating in adual connectivity mode, the wireless communication network comprising ofa first evolved NodeB (eNB) connected to a second eNB by an X2interface, wherein the UE is carrier aggregated with at least one firstserving frequency served by the first eNB and at least one secondserving frequency served by the second eNB. The method includes sendinga first Radio Resource Control (RRC) message to the UE by the first eNB.The method also includes, by the first eNB, receiving an indication fromthe second eNB, wherein the RRC message comprises one of instructions tothe UE to update security base key associated with the second eNB and tocheck a PDCP count associated with at least one Data Radio Bearer (DRB)established on at least one of the first eNB and the second eNB.

Also, provided herein is a wireless communication network including atleast one first evolved NodeB (eNB) connected to at least one second eNBby an X2 interface and at least one User Equipment (UE) operating in adual connectivity mode. The UE is carrier aggregated with at least onefirst serving frequency served by the first eNB and at least one secondserving frequency served by the second eNB. The first eNB is configuredfor sending a Radio Resource Control (RRC) message to the UE. The firsteNB receives an indication from the second eNB, wherein the RRC messagecomprises one of instructions to the UE to update security base keyassociated with the second eNB and to check a PDCP count associated withat least one Data Radio Bearer (DRB) established on at least one of thefirst eNB and the second eNB.

Provided herein is a first evolved NodeB (eNB) in a wirelesscommunication network. The first eNB is connected to at least one secondeNB by an X2 interface and at least one User Equipment (UE) operating ina dual connectivity mode. The UE is carrier aggregated with at least onefirst serving frequency served by the first eNB and at least one secondserving frequency served by the second eNB. The first eNB is configuredto send a first Radio Resource Control (RRC) message to the UE. Thefirst eNB receives an indication from the second eNB, wherein the RRCmessage comprises one of instructions to the UE to update security basekey associated with the second eNB and to check a PDCP count associatedwith at least one Data Radio Bearer (DRB) established on at least one ofthe first eNB and the second eNB.

Provided herein is a second evolved NodeB (eNB) connected to a wirelesscommunication network, wherein the second eNB is connected to at leastone first evolved NodeB (eNB) by an X2 interface and at least one UserEquipment (UE) operating in a dual connectivity mode. The UE is carrieraggregated with at least one first serving frequency served by the firsteNB and at least one second serving frequency served by the second eNB.The second eNB is configured to provide Data Radio Bearer (DRB) identityof at least one DRB established on at least one the second servingfrequency served by the second eNB and associated PDCP count values in aX2 message. The first eNB executes countercheck procedure towards the UEfor at least one DRB associated with the second eNB upon receiving asecond indication by the first eNB from the second eNB over the X2interface. The second indication indicates execution of countercheckprocedure for at least one DRB established on at least one the secondserving frequency served by the second eNB.

These and other aspects of the embodiments herein will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following descriptions, while indicatingpreferred embodiments and numerous specific details thereof, are givenby way of illustration and not of limitation. Many changes andmodifications may be made within the scope of the embodiments hereinwithout departing from the spirit thereof, and the embodiments hereininclude all such modifications.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an inter-evolved node B (eNB) carrier aggregation ina wireless communication network system according to embodiments of thepresent disclosure;

FIGS. 2A and 2B illustrate protocol architectures for dual connectivityunder consideration in 3GPP specification TR 36.842 according toembodiments of the present disclosure;

FIG. 3 illustrates an eNodeB according to embodiments of the presentdisclosure;

FIG. 4 illustrates a UE configured to operate in dual connectivity mode,according to embodiments of the present disclosure;

FIG. 5 illustrates an exemplary process of deriving KeNB_s* using pSCellparameters that are decided by SeNB according to embodiments of thepresent disclosure;

FIG. 6 illustrates an exemplary process of deriving KeNB_s* wherein thepSCell is decided by the MeNB, according to embodiments of the presentdisclosure;

FIG. 7 illustrates an exemplary process of MeNB initiated SCG releaseand subsequent addition of the SCG for SeNB key refresh due to wraparound of PDCP count of any PDCP entity handling the DRB in the SeNBaccording to embodiments of the present disclosure;

FIG. 8 illustrates an exemplary process of SeNB key refresh on the SeNBdeciding to change the PSCell according to embodiments of the presentdisclosure;

FIG. 9 illustrates an exemplary process of SCG release and additionprocedure, when MeNB key is changed, according to embodiments of thepresent disclosure;

FIG. 10 illustrates process of SeNB initiating the countercheckprocedure for SCG bearer and MeNB verifying the result, according toembodiments of the present disclosure;

FIG. 11 illustrates process of MeNB initiating the countercheckprocedure for SCG bearer and verifying the result, according toembodiments of the present disclosure; and

FIG. 12 illustrates process of SeNB initiating the countercheckprocedure for SCG bearer and verifying the result, according toembodiments of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 12, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged wireless communications system. Theembodiments herein and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. Descriptions of well-knowncomponents and processing techniques are omitted so as to notunnecessarily obscure the embodiments herein. Also, the variousembodiments described herein are not necessarily mutually exclusive, assome embodiments can be combined with one or more other embodiments toform new embodiments. The examples used herein are intended merely tofacilitate an understanding of ways in which the embodiments herein canbe practiced and to further enable those of skill in the art to practicethe embodiments herein. Accordingly, the examples should not beconstrued as limiting the scope of the embodiments herein.

Throughout the document, the terms “first evolved Node B” (first eNB),“Master eNB (MeNB)”, “primary eNB”, and “anchor eNB” are usedinterchangeably and may refer to a single eNB that connects a UserEquipment (UE) to the core network, which terminates at least S1-MMEinterface. Throughout the document, the terms “second eNB”, “SecondaryeNB (SeNB)”, “small eNB”, and “Drift eNB” are used interchangeably andmay refer to an eNB that serves the UE to enhance data throughput at theUE (but not the MeNB). Throughout the document, the terms “Second eNBChange Counter (SCC)”, “S-Count Counter (SCC)”, “Secondary CellCounter”, “Secondary Cell Group (SCG) Counter”, and SCG counter are usedinterchangeably and refer to a freshness parameter maintained at thefirst eNB for deriving SeNB base key. Throughout the document, the terms“refresh”, “rekeying” and “update” have been used interchangeably andmay refer to the derivation of a fresh security base key associated withthe SeNB. Throughout the document, the term “KeNB_m” or “KeNB_M” referto the key KeNB specified in 3GPP Technical Specification (TS) 33.401,which is used by the MeNB and the UE to derive further keys to protectthe communication between them and may also for derivation of SeNB basekey. Throughout the document, the term “KeNB_s”, “KeNB_S”, “KeNB_S*” and“KeNB_s*” refer to the key S-KeNB, which is used by the SeNB and the UEto derive further keys to protect the communication between them.Throughout the document, the term “serving cell configured with PUCCHresources”, “Special SCell”, “PSCell” and “pSCell” have been usedinterchangeably and may refer to at most one serving cell on at leastone second serving frequency served by the SeNB. Throughout thisdocument, the term “counter”, “PDCP COUNT”, “PDCP Sequence number” andmost significant parts of the PDCP COUNT values are usedinterchangeably.

Embodiments of the present disclosure achieve security in dualconnectivity mode of a User Equipment in a wireless communicationnetwork. Certain embodiments provided a method and system for creating asecure connection for the UE in a wireless network including the firsteNB connected to the second eNB. The UE is carrier aggregated with atleast one first serving frequency served by the first eNB and at leastone second serving frequency served by the second eNB. At the first eNB,a security base key associated with the second eNB is derived using afreshness parameter during at least for one of the following: additionof plurality of SCells within a second eNB, update of the security basekey of first eNB, update of the security base key of second eNB, changeof cryptographic algorithms and change of serving cell configured withPUCCH resources on, at most, one second serving frequency served by theSeNB. The security base key associated with second eNB is generatedbased on a security base key associated with the first eNB and afreshness parameter associated with the security context of the firsteNB. At the second eNB, a user plane encryption key is derived based onthe security base key associated with the second eNB received from thefirst eNB for encrypting data transfer over at least one data radiobearer established on at least one serving cell associated with thesecond eNB. The freshness parameter is informed to the UE for derivingthe security base key associated with the second eNB and furtherderiving a user plane encryption key for securing data transfer betweenthe UE and the SeNB. Further, the SeNB provides to the first eNB the DRBidentity and PDCP COUNT corresponding to at least one DRB established onat least one serving cell associated with second eNB to execute thecounter check procedure towards the UE.

Referring now to the drawings, and more particularly to FIGS. 1 through12, where similar reference characters denote corresponding featuresconsistently throughout the figures, there are shown preferredembodiments.

FIG. 1 illustrates an inter-evolved node B (eNB) carrier aggregation ina wireless communication network system 100 such as that of 3GPP's LongTerm Evolution (LTE), according to embodiments of the presentdisclosure. The embodiment of the wireless communication network system100 is for illustration only. Other embodiments could be used withoutdeparting from the scope of the present disclosure.

The wireless communication network system 100 includes a MobilityManagement Entity (MME) 102, a first eNB (MeNB) 104, a second eNB (SeNB)106, and a User Equipment (UE) 108 with inter-eNB carrier aggregation.The MME 102 manages session states, authentication, paging, mobilitywith 3GPP, 2G and 3G nodes, roaming, and other bearer managementfunctions. The UE 108 can be a mobile phone, a tablet, a wearablecomputing device, a communication dongle or any other device capable ofconnecting and communicating over a wireless communication networksystem 100. In certain embodiments, the UE 108 is capable of operatingin a dual connectivity mode of operation simultaneously connected to theMeNB 104 and the SeNB 106.

The MeNB 104 can be a macro eNB, a primary eNB, a first eNB, a anchoreNB or any other eNB capable of being a part of a wireless communicationnetwork system 100 and serving at least one cell served on a firstcarrier frequency (F1) to the UE 108. The SeNB 106 can be a secondaryeNB, a small eNB, a drift eNB or any other eNB capable of being a partof a wireless communication network system 100 and serving at least onecell served on a second carrier frequency (F2) to the UE 108. In certainembodiments, the MeNB and SeNB are parts of the same wirelesscommunication network system 100 and can be connected to each other atthe backend through a non-ideal backhaul such as X2 interface 110 andcommunicate using the X2 application protocol (X2-AP). The UE 108 isconfigured to be connected to at least one of the MeNB 104 and SeNB 106using an air interface. There can be plurality of SeNBs and MeNBspresent in the wireless communication network system 100. The wirelesscommunication network system 100 is only one example of a suitableenvironment and is not intended to suggest any limitation as to thescope of use or functionality of the disclosure.

In certain embodiments, the MeNB 104 is connected to the SeNB 106 withan interface characterized by one of a non-ideal backhaul link and anideal backhaul link. The UE 108 is carrier aggregated with at least onefirst serving frequency (F1) served by the MeNB 104 and at least onesecond serving frequency (F2) served by the SeNB 106 and configured tooperate in dual connectivity mode of operation in at least one of adownlink direction and an uplink direction with the MeNB 104 and SeNB106. In certain embodiments, the wireless communication network system100 uses a set of data radio bearers (DRBs) for the UE 108 that istransmitted over the MeNB 104, while another set of data radio bearers(DRBs) for the UE 108 is transmitted over the SeNB 106. When the MeNB104 and the SeNB 106 serve the UE 108, the MeNB 104 handles the controlplane of the UE 108 while the user plane handling of the UE 108 getseither distributed or split between the MeNB 104 and the SeNB 106.

FIGS. 2A and 2B illustrate protocol architectures for dual connectivityunder consideration in 3GPP specification TR 36.842, according toembodiments of the present disclosure. The embodiments of the protocolarchitectures shown in FIGS. 2A and 2B are for illustration only. Otherembodiments could be used without departing from the scope of thepresent disclosure.

FIG. 2A illustrates a core network (CN) split architecture from eNBperspective, according to embodiments of the present disclosure. TheS1-U terminates at the MeNB 104 and the SeNB 106. This architecture isreferred as core network (CN) split where a set of Evolved Packet System(EPS) bearers of the UE 108 are split in the core network at theService-Gateway (S-GW) and the EPS bearers are mapped on the respectiveS1-U interfaces towards the MeNB 104 and the SeNB 106. The respectiveEPS bearers are mapped on to corresponding data radio bearers (DRBs) ofthe MeNB 104 and the SeNB 106.

FIG. 2B illustrates Radio Access Network (RAN) split architecture fromeNB perspective, according to embodiments of the present disclosure. TheS1-U terminates only at the MeNB 104. This architecture is referred asradio access network (RAN) split where the EPS bearer #2 of the UE 108is split in the MeNB 104 and the offloaded bearer is mapped on the X2interface towards the SeNB 106. The layer 2 protocol stack for the dataradio bearer associated with the MeNB 104 (EPS Bearer #1 and Split EPSBearer #2) and the SeNB 106 (Offloaded EPS Bearer #2) includes anindependent PDCP entity per bearer at the MeNB, an independent RadioLink Control (RLC entity) per bearer at the MeNB 104 and SeNB 106, and acommon Medium Access Control (MAC) entity at the MeNB 104 and anindependent MAC entity at the SeNB 106. The split/offloaded data radiobearer associated with the MeNB 104 (EPS Bearer #2) and also associatedwith the SeNB 106 can be handled by the PDCP entity associated with MeNB104 called the common PDCP entity. Further, the MeNB 104 includes an RRCprotocol for control signaling. The layer 2 protocol stack associatedwith the MeNB 104 and SeNB 106 for handling the data radio bearersassociated with the MeNB 104 and SeNB 106, which includes the MACentity, the RLC entity. The PDCP entity as shown in FIG. 2A and FIG. 2Bis also duplicated at the UE 108 from the UE perspective and, hence, isnot shown explicitly for simplicity.

FIG. 3 illustrates an eNodeB (which can be at least one of a MeNB or aSeNB), according to embodiments of the present disclosure. Theembodiment of the eNB 300 shown in FIG. 3 is for illustration only.Other embodiments could be used without departing from the scope of thepresent disclosure. The eNB 300 shown in FIG. 3 can be either the MeNB104 or the SeNB 106. In certain embodiments, both the MeNB 104 and theSeNB 106 are configured the same as, or similar to, the eNB 300

The primary blocks present in an eNB 300 for communication in dualconnectivity of the UE 108 comprise a communication module 302, a bearerpath management module 304, a processor module 306, a memory module 308,and a key management module 310. In certain embodiments, thecommunication module 302 is configured to communicate securityinformation with the UE 108 and other eNBs for establishing a securitycontext. For example, the wireless communication module 302 in a MeNB104 can be configured to communicate the security base keys with one ormore UEs 108.

The bearer path management module 304 determines the bearer to betransmitted over within respective cells in the eNBs. The bearerdescribed herein can either be a Data Radio Bearer (DRB) or a SignalingRadio Bearer (SRB). The selection of a bearer can be based on aplurality of variables, which include, but are not limited to, Qualityof Service requirements (QoS), traffic characteristics of the bearer,load and coverage area of a selected secondary cell and so forth.

The key management module 310 is configured to derive or receive keys,or both, from a plurality of entities. In certain embodiments, the keymanagement module 310 is configured to generate further security keysbased on a received key. The MeNB 104 receives a base security key fromthe MME 102 and derives a security base key for SeNB 106. Similarly, theSeNB 106 uses the security key received from the MeNB 104 to derive newsecurity key to be used for secure communication with the UE 108. Thederived security base key for the SeNB 106 can be sent from the MeNB 104through the X2 interface using an X2 message.

Further, in certain embodiments, the memory module 308 is configured tostore data related to operation of the eNBs, such as operations of oneor both of MeNB 104 and SeNB 106, and the UE 108. The memory module 308can be configured to store various security keys generated forcommunication with different entities.

FIG. 4 illustrates a UE configured to operate in dual connectivity mode,according to embodiments of the present disclosure. However, UEs come ina wide variety of configurations, and FIG. 4 does not limit the scope ofthis disclosure to any particular implementation of a UE.

The primary blocks present in the UE 108 for communication in dualconnectivity include a communication module 402, a bearer pathmanagement module 404, a processor module 406, a memory module 408, anda key management module 410. In certain embodiments, the communicationmodule 402 is configured to communicate security information with theeNBs, such as MeNB 104, a SeNB 106, or both, for establishing a securitycontext. For example, the wireless communication module 402 in a UE 108can be configured to communicate protected user plane packets with oneor more eNBs. In certain embodiments, the wireless communication module402 in a UE 108 is able to communicate simultaneously with one or moreeNB s.

The bearer path management module 404 determines the bearer to betransmitted over within respective cells in the eNBs. The bearerdescribed herein can either be a Data Radio Bearer (DRB) or a SignalingRadio Bearer (SRB). The selection of a bearer can be based on aplurality of variables, which include, but are not limited to, Qualityof Service requirements (QoS), traffic characteristics of the bearer,load and coverage area of a selected secondary cell and so on.

The key management module 410 is configured to derive keys for aplurality of entities such as the eNBs and MME.

Further, the memory module 408 is configured to store data related tooperation of the eNBs, such as MeNB 104 and SeNB 106, and the UE 108.The memory module 408 can be configured to store various security keysgenerated for communication with different entities, as received by thekey management module 410.

Embodiments of the present disclosure provide a system and method toestablish security context for inter-eNB carrier aggregation.Specifically, certain embodiments provide a system and method for keyseparation and security handling between MeNB and SeNBs. The SeNB 106can include a key refresh flag in the SeNB release request messagetowards the MeNB. In certain embodiments, the SeNB 106 initiates a keyrefresh request message towards MeNB for refreshing KeNB_s key (based onevents such as PDCP wrap around, cryptographic algorithm to be changes,primary secondary Cell (pSCell) to be changed and like so). Also, incertain embodiments, the UE 108 initiates a key refresh request messagetowards MeNB for refreshing KeNB_s key. Consequently, the MeNB canindicate to the UE 108 the cell specific physical cell identity (PCI)and downlink frequency (EARFCN-DL) to be used as input parameter in keyderivation function (KDF) when more than one SCell is added during SeNBaddition procedure and PCI and EARFCN-DL is used as the inputparameters. In certain embodiments herein, a security contextestablishment is enabled between the SeNB 106 and the UE 108 using theRRC signaling between the UE 108 and the MeNB 104. In ceratinembodiments, assistance information is provided over the X2 interface inthe form of cell list and the associated RRM measurement (RSRP/RSRQmeasurements) meets the threshold criteria for qualifying to bepotential pSCell within the SCG; and assistance information is providedover the X2 interface in the form of cell list and the associatedphysical resource availability meets the criteria for qualifying to bepotential pSCell within the SCG.

Certain embodiments of the present disclosure provide a system andmethod for intruder detection in dual connectivity mode of operation ofuser equipment. Certain embodiments of the present disclosure provide amechanism for intruder detection for user plane traffic bearer of a UserEquipment (UE) in an inter-eNB carrier aggregation scenario. The methodincludes providing assistance information over the X2 interface relatedto DRB-ID and PDCP COUNT associated with DRB handled by the SeNB 106 forboth uplink and downlink DRBs, can include flagging DRB-IDs incountercheck request message either by MCG or SCG indication dependingon node handling the corresponding DRB.

Certain embodiments of the present disclosure disclose the MeNBinitiating the countercheck procedure for the DRB established in theMeNB and further; it can also include the DRBs established in the SeNB106.

Countercheck procedure can be supported for dual connectivity (for bothRAN Split architecture and CN Split) with the MeNB initiating theprocedure and verifying the result, the SeNB 106 initiating theprocedure and verifying the result, or the SeNB 106 initiating theprocedure and the MeNB verifying the result. From the above, the SeNB106 initiating the procedure and the MeNB verifying the result can be apreferred procedure, since SeNB is handling the PDCP entity and the MeNBneeds to be the decision making entity.

For initial SeNB addition procedure, the SeNB key derivation is based oncurrent MeNB key in use (KeNB_m). The process, as depicted herein uses aSeNB Counter Count (S-Count or SCC) to ensure that SeNB key repetitiondoes not occur. The specific parameters of the reference cell (pSCell)from the group of SCell (SCG cells) handled by the SeNB 106 also can beused in the SeNB key derivation.

The UE 108 sends the measurement report to the MeNB 104. The SeNB 106also sends the resource status update to the MeNB 104 using the X2interface. The resource status update includes the load information,radio problem and so forth. Based on information received from the UE108 and the SeNB 106, the MeNB 104 selects the reference cell (pSCell).The MeNB 104 sends a SCellCommand to the SeNB 106, wherein theSCellCommand includes the ID of the selected pSCell to add or release,restrictions (if any) associated with the pSCell and so forth. The SeNB106 sends a SCellConfig message to the MeNB 104 upon receiving theSCellCommand, wherein the SCellConfig includes an ScellToAddModList,security algorithm and so forth. The MeNB 104 sends anRRCConnectionReconfiguration message to the UE 108, wherein theRRCConnectionReconfiguration message includes a security configurationfor the selected pSCell. In response to the RRCConnectionReconfigurationmessage, the UE 108 sends a response to the MeNB 104 in the form of anRRCConnectionReconfigurationComplete message. The MeNB 104 also sends aRACH (Random Access Channel) message to both the UE 108 and the SeNB106. The MeNB 104 and the UE 108 generate a fresh SeNB key-chain(S-Count) thatincrements the S-Count. The MeNB 104 further sends aSCellConfigACK message to the SeNB 106, wherein the SCellConfigACKmessage includes an SeNB-Kenb (KeNB_S). In response, the SeNB 106 sendsa SCellCommandAck response to the MeNB 104.

The counter as disclosed herein is a special case of a nonce. A Nonceand Counter (S-Count or SCC) have been used interchangeably herein. Thecounter is incremented for every SeNB addition and in case of nonce, anew nonce is pseudo randomly generated for every SeNB addition.

The key derived for the SeNB 106 is applicable for all user planetraffic handled by all the SCells added in the SeNB 106. The terms MeNBkey and MCG key and the terms SeNB key and SCG key have been usedinterchangeably herein.

Embodiments herein disclose a mechanism to retain old key in the SeNB106 or refresh the new key in the SeNB 106, when KeNB_m is refreshedeither due to change in the MeNB 104 or PDCP count of any PDCP entity inthe MeNB 104 is about to wrap around.

Embodiments herein disclose a mechanism to avoid KeNB_s key change whenmultiple SCells are configured for the UE 108 and the special SCell fora particular UE 108 is changed.

FIG. 5 illustrates an exemplary process of deriving KeNB_s* using pSCellparameters that are decided by the SeNB 106 according to embodiments ofthe present disclosure.

When multiple SCells are added simultaneously, the pSCell is the one onwhich the UE 108 performs random access. Upon deciding the pSCell, theSeNB 106 sends a SeNB Key request message to the MeNB 104 on the X2interface providing the pSCell or the cell specific parameters. The MeNB104 generates the KeNB_s* based on the indicated pSCell or cell specificparameters. The KeNB_s* is provided to the SeNB 106 in SeNB key responsemessage.

Upon the MeNB 104 deciding to add a SeNB 106 502, the MeNB 104 sends aSeNB add request 504 to SeNB 106, wherein multiple SCells can be addedbased on the add request. The SeNB 106 sends a SeNB Add Response 508message indicating the decided pSCell 506 from the plurality of addedSCells, in response to the add request 504. Upon receiving the responsemessage 508, the MeNB 104 stops LCH_s 510. The LCH_S or LCH_s isassociated with the logical channel between the UE 108 and the SeNB 106.The LCH_S or LCH_s corresponds to the SCG bearers. The MeNB 104 sends aSeNB Add Acknowledgement 511 to SeNB 106. The MeNB 104 then sends aRRCConnectionReconfiguration message 512 to the UE, wherein theRRCConnectionReconfiguration message indicates that a new SeNB 106 hasbeen added, multiple SCells have been added, the necessary parametersrequired for the key derivation (SCC), the pSCell and so on. Uponreceiving the RRCConnectionReconfiguration message 512, the UE 108 stopsthe LCH_s 514 and sends a RRCConnectionReconfigurationComplete message516 to the MeNB 104. In parallel, the MeNB 104 sends a SN Status message518 to the SeNB 106. The MeNB 104 also starts forwarding data 520 to theSeNB 106. The UE 108 generates KeNB_s 522, based on parameters relatedto the PSCell, as communicated by the MeNB 104. The UE 108 performsrandom access 524 on one of the SCells from the plurality of addedSCells, wherein the Scell on which the UE performs the random accessprocedure 524 is the PSCell indicated in theRRCConnectionReconfiguration message 512 from the MeNB 104. The UE 108further starts LCH_s 526 for the added SCells. The MeNB 104 generatesKeNB_s*, based on parameters related to the pSCell. The MeNB 104 thensends a SeNB Key (KeNB_s*) to the SeNB 106 in the SCG AddAcknowledgement message. Using KeNB_s* as KeNB_s 528, the SeNB 106starts LCH_s 530. Also, the UE 108 and the MeNB 104 consider KeNB_M ask1 and k1 is applied for LCH_M 532. The LCH_M or LCH_m can be associatedwith the logical channel between the UE and the MeNB. The LCH_M or LCH_mcorresponds to the MCG bearers. Also, the UE 108 and the SeNB 106consider KeNB_S as k2 and k2 is applied for LCH_S 534. The MeNB 104shares the PDCP (Packet Data Convergence Protocol) status report 536with the SeNB 106 and the UE 108. The UE 108 and the SeNB 106 startusing the new KeNB_s 540 to derive further keys, which can be used forprotecting the user plane traffic of all SCells.

In certain embodiments, a method deriving the KeNB_s key independent ofcell specific parameters is disclosed. According to this embodiment, thekey derivation function independent of the cell specific parameterscomprises:

KeNB_s*=KDF{KeNB_m(in use),Random Seed,KeNB_s,<other possibleparameters>}

where the random seed could be a Nonce or/and a counter or/and PDCPCOUNT of the PDCP entity handling the signaling bearer (SRB0 or SRB1) inthe MeNB 104, which initiates the Key change in the UE 108. Here theKeNB_s* is derived not using any cell specific parameter. In the abovekey derivation function, other than Random seed and KeNB_m, all otherparameters are optional.

If the Key derivation function (KDF) does not include PCI and EAFRCN-DL,which are cell specific parameters (but a random parameter like “Nonceor Counter or PDCP COUNT, or a combination thereof,” and so on), eventhen if more than one SCell is added simultaneously, there would be nosecurity issue in deriving cryptographically separate keys.

In certain embodiments, one of the <other possible parameters>mentionedin the key derivation function can be eNB ID of the SeNB 106 broadcastedin the SIB1 signaling message for KeNB_S* derivation. The eNB ID isalready included in SIB1. The general understanding is that the 20 MSBof this 28 bit field identify the eNB.

In LTE up to Rel-11, upon every handover (HO) and re-establishment, theUE 108 derives new access stratum (AS) keys, such as KeNB, K_RRCint,K_RRCenc and K_UPenc. It is reasonable to assume the SeNB keys need tobe updated whenever the MeNB key changes. Therefore the SeNB keys needto be updated upon MeNB key change, but whether this would result in SCGrelease and addition need to be considered. Given that MeNB 104 handover(HO) may be time critical, it may actually be preferable to release theSCG upon MeNB HO and re-establish it after HO completion. In certainembodiments, the release of SCG and subsequent addition would be similarto the user plane procedures during HO but restricted to SCG bearers,namely MAC entity handling the SCG is reset, PDCP entity isre-established and RLC entity is re-established.

In certain embodiments of the present disclosure, the SCG release andsubsequent addition is a simple approach applicable for both SCG keyrefresh and MeNB key change due to MeNB handover (HO) or due to wraparound of the PDCP count of any PDCP entity handling the DRB in the MeNB104 or in SeNB 106.

FIG. 6 illustrates an exemplary process of deriving KeNB_s* using pSCellparameters, wherein the MeNB decides the PSCell, according toembodiments of the present disclosure.

When multiple SCells are added simultaneously, the pSCell is the one onwhich the UE 108 performs random access. The MeNB 104 generates theKeNB_s* based on the decided pSCell or cell specific parameters.

When the MeNB 104 decides 602 to add a SeNB 106, the MeNB 104 decidesthe PSCell and derives the KeNB_s*. The MeNB 104 sends a SeNB addrequest 604 to SeNB 106, wherein the add request can comprise ofmultiple SCells to be added, the decided PSCell and the derived KeNB_s*.The SeNB 106 sends a SeNB Add Response message 606, in response to theadd request. Upon receiving the response message 606, the MeNB 104 stopsLCH_s 608. The MeNB 104 then sends a RRCConnectionReconfigurationmessage 612 to the UE, wherein the RRCConnectionReconfiguration message612 indicates that a new SeNB 106 has been added, multiple SCells havebeen added and so forth. upon receiving the RRCConnectionReconfigurationmessage 612, the UE 108 stops the LCH_s 614. The UE 108 generates KeNB_s616, based on parameters related to the pSCell, as communicated by theMeNB 104 and sends a RRCConnectionReconfigurationComplete message 618 tothe MeNB 104. In parallel, the MeNB 104 sends a SN Status message 620 tothe SeNB 106, wherein the SeNB 106 includes the count. The MeNB 104 alsostarts forwarding data 622 to the SeNB 106. The UE 108 performs randomaccess 624 on one of the SCell from the plurality of added SCells,wherein the Scell on which the UE performs the random access procedureis the pSCell indicated in the RRCConnectionReconfiguration message 618from the MeNB 104. The UE 108 further starts LCH_s 625 for the addedSCells. Using KeNB_s* as KeNB_s 626, the SeNB 106 starts LCH_S 628.Also, the UE 108 and the MeNB 104 consider KeNB_M as k1 and k1 isapplied 630 for LCH_M. Also, the UE 108 and the SeNB 106 consider KeNB_Sas k2 and k2 is applied 632 for LCH_S. The MeNB 104 shares the PDCP(Packet Data Convergence Protocol) status report 634 with the SeNB 106and the UE 108. The UE 108 and the SeNB 106 start using the new KeNB_s636 for the user plane traffic of all SCells.

FIG. 7 illustrates an exemplary process of MeNB initiated SCG releaseand subsequent addition of the SCG for SeNB key refresh due to wraparound of PDCP count of any PDCP entity handling the DRB in the SeNB,according to embodiments of the present disclosure.

The SCG release and subsequent addition of the same SCG, namely SCGrelease and addition procedure, means, the user plane protocol stackassociated with the SeNB 106 is reset and reestablished 702 in the UE108 and in the SeNB 106. The SeNB 106 sends a Resource Status Update(X2-AP status update) message 704 to the MeNB 104, wherein the ResourceStatus Update comprises of PDCP SN wrap-around status. In an embodiment,the X2-AP status update message 704 is a SeNB 106 modification requiredmessage with SCG Change Indication having a cause value as PDCP CountWrap Around. Upon receiving the SeNB modification required message, theMeNB 104 derives a new KeNB_s* 706. The MeNB 104 sends a SCell Commandmessage (X2-AP message 708, for example, SeNB modification request)comprising of the new KeNB_s* to the SeNB 106. The MeNB 104 furthersends the RRCConnectionReconfiguration message 710 to the UE 108. TheMeNB 104 includes the necessary parameters (SCC) in theRRCConnectionReconfiguration for the UE 108 to update the KeNB_s. Uponreceiving this message, the UE 108 updates (derives) the key KeNB_s andsends the RRCConnectionReconfigurationComplete message 712 to the MeNB104. The UE 108 releases 714 the active key KeNB_s and re-establishes alayer 2 protocol stack. To re-establish a layer 2 protocol stack means,the UE 108 resets the MAC layer associated with the SeNB 106 andre-establishes the PDCP and the RLC entities associated with the SeNB106 for each DRB established between the UE 108 and the SeNB 106. TheSeNB 106 also releases 716 the old KeNB_s key. MeNB 104 then sends theSCellConfigAck 718 to the SeNB 106 and receives a SCellCommandAck 719from the SeNB 106. Then the UE 108 performs random access 720 on one ofthe SCell from the plurality of added SCells, wherein the Scell on whichthe UE performs the random access 720 procedure is the pSCell indicatedin the RRCConnectionReconfiguration message 710 from the MeNB. The SeNB106 further uses the KeNB_s* 722, as received from the MeNB 104 as theKeNB_s. The UE 108 and the SeNB 106 start using 724 the new key derivedfrom the updated (new) KeNB_s for the user plane traffic protection ofall SCells.

If there is a requirement, trigger, or event to change the SCG securityalgorithm to the existing DRB between the UE 108 and the SeNB 106, thenit would be reasonable to support it only by means of SCG release andaddition procedure. In certain embodiments, the SeNB 106 sends a SeNBmodification required message to the MeNB 104 and with SCG ChangeIndication having a cause value as security algorithm change (or thecause value can be as “others”). In certain embodiments, the SeNBmodification required message carry the selected security algorithm. Itshould be noted that, based on the cause, indication, or informationfrom the SeNB (for example, in the SeNB modification required message),the MeNB does not initiate the user plane path switch procedure with theEPC, but initiates the key change procedure with algorithm change bymeans of SCG release and addition procedure.

FIG. 8 illustrates an exemplary process of SeNB key refresh on the SeNBdeciding to change the PSCell, according to embodiments of the presentdisclosure.

The user plane protocol stack associated with the SeNB 106 is reset andreestablished 802 in the UE 108 and in the SeNB 106. The UE 108 sendsmeasurement report 804 to the MeNB 104, for different frequencies, whichhave been configured on the UE 108. The MeNB 104 sends a SeNBmodification request message (X2-AP) 806 to the SeNB 106, wherein theSeNB modification message 806 can include RRM measurements. Based uponthe SeNB modification request message 806, the SeNB 106 decides tochange the PSCell 810 and decides on an appropriate PSCell. Upondeciding to change the PSCell, the SeNB 106 sends a SeNB modificationresponse message 812 to the MeNB 104, wherein the SeNB modificationresponse message includes the new PSCell or cause, indication, orinformation, or a combination thereof, that it is for pSCell change, asdetermined by the SeNB 106. The MeNB 104 derives 814 a new KeNB_s* andsends a SeNB modification acknowledge message 816, including the derivedKeNB_s*, to the SeNB 106. The MeNB 104 further sends theRRCConnectionReconfiguration message 818 to the UE 108. Upon receivingthis message, the UE 108 sends the RRCConnectionReconfigurationCompletemessage 820 to the MeNB 104. The MeNB includes the necessary parameters(SCC) in the RRCConnectionReconfiguration required for the UE to updatethe KeNB_s. The UE 108 derives the new KeNB_s and releases 821 the oldkey and re-establishes a layer 2 protocol stack. The SeNB 106 alsoreleases 822 the old key. The MeNB 104 then sends the SCellConfigAck 824to the SeNB 106 and receives a SCellCommandAck 826 from the SeNB 106.Then the UE 108 performs random access 828 on one of the SCell from theplurality of added SCells, wherein the Scell on which the UE performsthe random access 828 procedure is the pSCell indicated in theRRCConnectionReconfiguration message from the MeNB. The SeNB 106 furtheruses the KeNB_s* 830, as received from the MeNB 104 as the KeNB_s toderive further keys. The UE 108 and the SeNB 106 start using 832 thenewly derived key from the updated KeNB_s for securing the user planetraffic of all SCells.

FIG. 9 illustrates an exemplary process of SCG release and additionprocedure, when MeNB key is changed, according to embodiments of thepresent disclosure.

The user plane protocol stack associated with the SeNB 106 is reset andreestablished 902 in the UE 108 and in the SeNB 106. When the MeNB 104decides to refresh 904 the KeNB, the MeNB 104 updates 906 the KeNB_m andderives the new KeNB_s*. The MeNB 104 sends a SeNB modify message 908(comprising of the derived KeNB_s*) to the SeNB 106. The MeNB 104further sends the RRCConnectionReconfiguration message 910 to the UE108. The MeNB includes the necessary parameters (SCC) in theRRCConnectionReconfiguration message 910 for the UE to update theKeNB_s. Upon receiving RRCConnectionReconfiguration message 910, the UE108 sends the RRCConnectionReconfigurationComplete message 912 to theMeNB 104. The UE 108 performs the key refresh procedure (updates theKeNB_M) and then the UE 108 derives the new KeNB_s and releases 914 theold key and re-establishes a layer 2 protocol stack. The SeNB 106 alsoreleases 915 the old key. MeNB 104 then sends the SCellConfigAck 916 tothe SeNB 106 and receives a SCellCommandAck 917 from the SeNB 106. Thenthe UE 108 performs random access 918 on one of the SCell from theplurality of added SCells, wherein the Scell on which the UE performsthe random access 918 procedure is the pSCell indicated in theRRCConnectionReconfiguration message 910 from the MeNB. The SeNB 106further uses the KeNB_s* 920, as received from the MeNB 104 as theKeNB_s to derive further keys. The UE 108 and the SeNB 106 start using922 the newly derived key from the updated KeNB_s for securing the userplane traffic of all SCells.

FIG. 10 illustrates process of SeNB initiating the countercheckprocedure for SCG bearer and MeNB verifying the result, according toembodiments of the present disclosure.

Data bearer 1001 handled by MeNB 104 in dual connectivity is establishedbetween UE 108 and MeNB 104. Data bearer 1002 handled by SeNB 106 indual connectivity is established between UE 108 and SeNB 106. The SeNB106 initiates countercheck 1003 towards the UE 108 for SCG bearers overthe X2 interface. The trigger for the SeNB 106 to initiate thecountercheck 1003 procedure can be periodical, wherein a periodicalcountercheck 1003 procedure occurs at regular time intervals. Thetrigger for the SeNB 106 to initiate the countercheck 1003 procedure canbe event based, such as if there is sudden surge in volume of data. Thetrigger for the SeNB 106 to initiate the countercheck 1003 procedure canbe when considered necessary (similar to other SCG bearers). The triggerfor the SeNB 106 to initiate the countercheck 1003 procedure can be tocheck volume of data transfer. If the countercheck procedure istriggered, the SeNB 106 sends the contents (like PDCP count valuesand/or DRB IDs) in a counter check message 1004 to the MeNB 104 over theX2 interface. The SeNB 106 can also indicate to the MeNB 104 the currentUL/DL PDCP COUNT status of the DRB and the associated DRB-ID (outsidethe RRC container). The SeNB 106 can also indicate an expected (PDCPsequence number) SN rate in coming seconds (again outside the RRCcontainer) and so on. The MeNB 104 executes 1006 the RRC proceduretowards the UE 108 and stores the information received from the SeNB 106for verification. The UE 108 may verify the result based on theinformation received. The UE 108 compares the PDCP COUNT values receivedin the Countercheck message with the values of its radio bearers. The UE108 may include different UE PDCP COUNT values for all the establishedDRBs (MCG DRB as well as SCG DRB) within the Countercheck Responsemessage, if the value received and its current PDCP values are notmatching (may be within acceptable window size). When the MeNB 104receives the response 1008 from the UE 108, the MeNB 104 performs thecountercheck 1010 based on the information provided by the SeNB 106. Ifthe MeNB 104 receives a response message 1008 from the UE 108 that doesnot contain any PDCP COUNT values, then the MeNB 104 considers thecountercheck as passed. If the countercheck is passed, then there is nointrusion detected 1011. That is, if the MeNB 104 determines 1012 thatthe count is not in range, an intruder attack is detected on the MCGbearer 1014 or an intruder attack is detected on the SCB bearer 1016. Ifthe MeNB 104 receives a response that contains one or several PDCP COUNTvalues from the UE, then the MeNB 104 considers the countercheck as notpassed (the UE can include the PDCP COUNT which are different comparedto the values received from the MeNB). If the countercheck is notpassed, then there is an intrusion detected. Then, the MeNB 104 alertsthe SeNB 106 and takes appropriate action like initiating request forreleasing the SCG 1018, releasing the UE 1020 and so forth.

FIG. 11 illustrates process of MeNB 104 initiating the countercheckprocedure for SCG bearer and verifying the result, according toembodiments of the present disclosure.

Data bearer 1101 handled by MeNB 104 in dual connectivity is establishedbetween UE 108 and MeNB 104. Data bearer 1102 handled by SeNB 106 indual connectivity is established between UE 108 and SeNB 106. The MeNB104 initiates the countercheck procedure 1103 towards the UE 108 for SCGbearers. The trigger for the MeNB 104 to initiate the countercheckprocedure can be periodically, wherein a periodical check procedureoccurs at regular time intervals. The trigger for the MeNB 104 toinitiate the countercheck procedure can be event based such as if thereis sudden surge in volume of data. The trigger for the MeNB 104 toinitiate the countercheck procedure can be when considered necessarysimilar to other MCG bearers. The trigger for the MeNB 104 to initiatethe countercheck procedure can be to check volume of data transfer. Ifthe countercheck procedure is triggered, the MeNB 104 requests 1106 theSeNB 106 for counter information for SCG bearer and the associatedDRB-ID over the X2 interface of that UE 108. The SeNB 106 provides 1108the current UL/DL sequence number (SN) status and the DRB-ID of the DRBsof that UE 108 in X2 message sent in response. Further, the MeNB 104executes countercheck procedure 1110 towards the UE 108 and may beflagging the DRB-ID with MCG or SCG indication. The indication can be atleast one of the following: a bit indication for the correspondingDRB-ID, a distinguished list of DRB-IDs of the MCG and SCG, PCIindication for the corresponding DRB-ID, PCI and EARFCN-DL for thecorresponding DRB-ID, Global cell ID, Cell Global identifier and so on.The UE 108 compares the PDCP COUNT values received in the Countercheckmessage with the values of its radio bearers. The UE 108 may includedifferent UE PDCP COUNT values for all the established DRBs (MCG DRB aswell as SCG DRB) and may be flagging the DRB-ID with MCG or SCGindication within the Countercheck Response message 1112. When the MeNB104 receives the Countercheck Response message 1112 from the UE 108, theMeNB 104 performs the countercheck 1113 based on the informationprovided by the SeNB 106. If the MeNB 104 receives a countercheckresponse message 1112 that does not contain any PDCP COUNT values, thenthe countercheck is passed 1115. That is, if the MeNB 104 determines1114 that the count is not in range, an intruder attack is detected onthe MCG bearer 1116 or an intruder attack is detected on the SCB bearer1118. If the countercheck is passed, then there is no intrusiondetected. If the MeNB 104 receives a countercheck response that containsone or several PDCP COUNT values, then the countercheck is not passed(the UE include the PDCP COUNT which are different compared to thevalues received from the MeNB). If the countercheck is not passed, thenthere is an intrusion detected. The MeNB 104 alerts 1120 the SeNB 106,if the mismatched PDCP COUNT of the DRB belongs to SCG and MeNB 104takes appropriate action such as releasing the SCG, reporting to theCore Network entities to take appropriate action, releasing the UE 1122,and so forth.

Here, the MeNB 104 is in full control of handling the countercheckprocedure since initiation and termination of the procedure is underMeNB 104 control. For Split bearers (RAN Split architecture as depictedin FIG. 2B) it can be assumed that the SeNB 106 applies the same DRBidentity (DRB-ID) for split bearers as used by the MeNB 104 i.e. theMeNB 104 decides the identity for Split bearer. This can be applicableto SCG DRBs also where the MeNB 104 controls the entire procedure.

In certain embodiments, the UE 108 verifies and provides its countervalues to the MeNB 104 over the RRC signaling for the MeNB or SeNB toverify and act.

In certain embodiments, the UE 108 verifies the count values received incountercheck request message and if the countercheck fails (the UE 108itself detects intrusion attack), then the UE 108 sends the modifiedcountercheck response message to the MeNB 104 that it has detectedintrusion attack for SCG bearer. The MeNB 104 decides the release of theSCG and/or SCG bearer for which intrusion is detected.

In another embodiment, upon detecting intrusion attack, the UE 108 sendsthe modified countercheck response message to the MeNB 104 that it hasdetected intrusion attack for the SCG bearer and informs the MeNB 104that the UE 108 is releasing the SCG bearer. After sending thecountercheck response message, the UE 108 autonomously takes thedecision to release the SCG bearer.

FIG. 12 illustrates process of SeNB initiating the countercheckprocedure for SCG bearer and verifying the result, according toembodiments of the present disclosure.

Data bearer 1201 handled by MeNB 104 in dual connectivity is establishedbetween UE 108 and MeNB 104. Data bearer 1202 handled by SeNB 106 indual connectivity is established between UE 108 and SeNB 106. The SeNB106 initiates the countercheck 1204 towards the UE 108 for SCG bearersover the X2 interface. The trigger for the SeNB 106 to initiate thecountercheck procedure can be at periodical, wherein a periodical checkprocedure occurs at regular time intervals. The trigger for the SeNB 106to initiate the countercheck procedure can be event based such as ifthere is sudden surge in volume of data. The trigger for the SeNB 106 toinitiate the countercheck procedure can be when considered necessarysimilar to other SCG bearers. The trigger for the SeNB 106 to initiatethe countercheck procedure can be to check volume of data transfer. Ifthe countercheck procedure is triggered, the SeNB 106 sends the contents(PDCP Count) in a countercheck message 1206 to the MeNB 104 over the X2interface. The MeNB 104 transparently executes 1208 an RRC procedure tothe UE 108 by forwarding the countercheck message received from the SeNB106 to the UE 108. The UE 108 verifies the result based on theinformation received. The UE 108 compares the PDCP COUNT values receivedin the Countercheck message with the values of its radio bearers. The UE108 may include different UE PDCP COUNT values for all the establishedDRBs (MCG DRB as well as SCG DRB) within the Countercheck Responsemessage 1210. MeNB verifies 1211 a result based on the CountercheckResponse message 1210 for the MCG bearers. When the MeNB 104 receivesthe Countercheck Response message 1210 from the UE, the MeNB 104forwards 1212 the response message on X2 interface to the SeNB 106 in atransparent manner. The SeNB 106 verifies 1214 the result based on theinformation forwarded by the MeNB 104. If the SeNB 106 receives acountercheck response message that does not contain any PDCP COUNTvalues, then the SeNB 106 considers the countercheck as passed. If thecountercheck is passed, then there is no intrusion detected 1216. If theSeNB 106 receives a countercheck response that contains one or severalPDCP COUNT values, then the SeNB 106 considers the countercheck as notpassed (the UE include the PDCP COUNT which are different compared tothe values received from the MeNB). If the countercheck is not passed,then there is an intrusion detected 1218. Then, if the mismatched PDCPCOUNT of the DRB belongs to SCG, the SeNB 106 takes appropriate actionlike initiating request for releasing the SCG 1220, report to the CoreNetwork entities via the MeNB to take appropriate action and so on.

The countercheck procedures can be used interchangeably, two or morecountercheck procedures can be merged, or a combination of merging andinterchanging of procedures can be used as required.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and/or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for performing a change of a servingcell group (SCG) by a secondary base station in a wireless communicationsystem supporting a dual connectivity of a user equipment, the methodcomprising: transmitting, by the secondary base station for the dualconnectivity, a message including information indicating the change ofthe SCG to a master base station for the dual connectivity, to requestthe change of the SCG; and receiving, by the secondary base station, asecurity key associated with the secondary base station, the securitykey being refreshed by the change of the SCG, wherein the informationindicating the change of the SCG comprises information representingwraparound of a packet data convergence protocol (PDCP) count at thesecondary base station.
 2. The method of claim 1, wherein theinformation indicating the change of the SCG comprises informationrepresenting a change of primary secondary cell (PScell) of the SCG. 3.The method of claim 1, wherein the master base station and the secondarybase station comprise a medium access control (MAC) entity, a radio linkcontrol (RLC) entity, and a PDCP entity which are configured for theSCG, respectively, wherein the MAC entity handling the SCG is reset andthe PDCP entity and the RLC entity are re-established by the change ofthe SCG.
 4. The method of claim 1, wherein the change of the SCGcomprises at least one of addition or release of at least one cell inthe SCG.
 5. A secondary base station capable of performing a change of aserving cell group (SCG) in a wireless communication system supporting adual connectivity of a user equipment, the secondary base stationcomprising: a communication interface configured to communicate withother network entity; and a controller configured to controltransmitting a message including information indicating the change ofthe SCG to a master base station for the dual connectivity, to requestthe change of the SCG, and receiving a security key associated with thesecondary base station, the security key being refreshed by the changeof the SCG, wherein the information indicating the change of the SCGcomprises information representing wraparound of a packet dataconvergence protocol (PDCP) count at the secondary base station.
 6. Thesecondary base station of claim 5, wherein the information indicatingthe change of the SCG comprises information representing a change ofprimary secondary cell (PScell) of the SCG.
 7. The secondary basestation of claim 5, wherein the master base station and the secondarybase station comprise a medium access control (MAC) entity, a radio linkcontrol (RLC) entity, and a PDCP entity which are configured for theSCG, respectively, wherein the MAC entity handling the SCG is reset andthe PDCP entity and the RLC entity are re-established, by the change ofthe SCG.
 8. The secondary base station of claim 5, wherein the change ofthe SCG comprises at least one of addition and release of at least onecell in the SCG.